Gear pumps



July 20, 1965 s. WOOD 3,195,469

GEAR PUMPS Filed Oct. 11, 1963 v 3 Sheets-Sheet 1 R5. Wood IN VE/WUR A TT'ORNE 7 July 20. 1965 Filed Oct. 11, 1963 R. S. WOOD 3 Sheets-Sheet 2 July 20, 1965 R. s. WOOD 3,195,469

GEAR PUMPS Filed Oct. 11, 1965 5 Sheets-Sheet 3 R. 5. Wood INVENTOR A TTORIVE Y United States Patent 3,195,469 GEAR PUMPS Robert Spurgeon Wood, Alverstoire, Gosport, England,

assignor to The Piessey Company (UK) Limited, llford, England, a company of Great Britain Filed Get. 11, 1963, Ser. No. 315,721 Claims priority, appiication Great Britain, Get. it, 1962, 33,468/62 2 Claims. (Cl. 103-126) This invention relates to gear pumps of the kind in which side plates, loaded by the action of pump-delivery pressure, are employed to increase the volumetric efficiency of the pump and has for an object to provide an improved gear pump of the kind specified adapted to maintain high volumetric efficiency for a relatively long time. This makes the invention particularly valuable for pumps intended to deliver liquid of low viscosity and/or poor lubricating qualities, especially where the liquid is to be delivered against considerable pressure.

In operation of a gear pump the part of the circumference of each gear which travels from the suction side to the delivery side of the pump is subjected to a hydrostatic pressure which rises gradually as each tooth gap approaches the delivery side, and this phenomenon in conjunction with the inherent difference of pressure between the inlet chamber and the delivery chamber of the pump results in a tendency of the gears, as a result of play in the bearings and resilient deflection of the gear shafts, to make metallic contact with the housing at the low-pressure side of the housing. Herein the delivery chamber is the chamber accommodating that part of each gear which travels on the delivery side from the point of sealing contact with the housing to the point of intermesh and the inlet chamber is the chamber accommodating that part of each gear which travels on the inlet side from the point of intermesh to the point at which the tooth gaps become sealed by contact with the housing. In practice this tendency is utilised in pumps of the kind specified to cause, during so-called runningin of the gear pumps, due to initial wear, the housing surfaces at the low pressure side to become very intimately conform with the co-operating gear surface with resultant excellent sealing qualities at the end of the running-in period. In pumps delivering liquids of good lubricating qualities this excellent sealing contact will be maintained for a long time, but ditficulties arise in pumps employed for delivering liquids of poor lubricating qualities such as wide-out gasoline, in which wear of the internalparts of the pump is liable to a major limitation in the operating life of the pump.

According to the present invention the life of the pump can be considerably extended if the pump housing is made symmetrical in such manner that when one side of the pump housing has become worn so as to unduly affect the seal between the pump housing and the tips of the gear teeth, the pump can be dismantled and reassembled With the housing turned by 180 so as to interchange the inlet and outlet sides of the housing body. The above-mentioned unbalance of pressure will then cause the gears to make contact with the wall of the gear housing at the side which previously was the highpressure side, and after a new running-in period the original quality of seal will be substantially restored. In order to permit this reversal, the housing must be symmetrical in relation to two mutually perpendicular planes of symmetry one of which is preferably the plane containing the axes of the'two gears. If the housing is symmetrical in relation both to that plane and to a plane perpendicular'to the said plane and parallel to the gear axes, the result can be achieved alternatively either by turning the housing in it own plane or by turning it about ddhSAhfi Patented July 20, 1965 an axis perpendicular to the last-mentioned plane of symmetry. Thus the invention may be broadly stated to be characterised by the fact that the housing body is symmetrical about at least two of three mutually perpendicular planes of which one contains the axes of the said gears and another is parallel to the said axes, so that the gears can be assembled with the housing body in at least two alternative positions in which the housing is turned relative to the gears about the line of intersection of two planes of symmetry.

Wear is also liable to occur at the tooth flanks, however, and in order to reduce this wear, or at least to distribute it more uniformly so as to delay the increase in leakage through the zone of intermesh, the pump is preferably, according to another feature of the invention, equipped with intermeshing pumping gears having numbers of teeth which are prime relative to each other, the number of teeth differing, for example, by a single tooth. It will be appreciated that this construction will make it impossible to preserve the last-mentioned symmetry but, as already stated, the reversibility feature can still be employed by turning the pump body in the second one of the two methods above referred to.

The invention is preferably employed in combination with other features which contribute to high volumetric efiiciency of the pump, more particularly in combination with the use of pressure-loaded side plates which are applied to the side surfaces of the gears by the delivery pressure of the pump, and in which substantial alignment of the pressure forces acting on the two sides of each side plate is achieved by means of a sealing ring or gasket which separates a zone in which pump deliver pressure acts from a second zone under pump inlet pressure. This ring or gasket is accommodated in a surface groove of the side plate, but in order to separate those zones, the sealing ring or gasket must pass across the peripheral edge of the side plate or plates into contact with the side surface of the housing so that one of the inlet and outlet chambers of the pump is inside the area encircled by the sealing ring and the other outside. According to the invention to permit the pump body to be reversed in the manner stated without abandoning this sealing ring feature, two grooves adapted to accommodate the portion of the sealing ring between the two points at which it crosses the edge of the, or each side plate are formed in the housing body at the two positions respectively required for assembly before and after reversal of the pump housing body.

In order that the invention may be more readily understood, an embodiment will now be described with reference to the accompanying drawings, in which FIGURE 1 is an axial section of the gear pump according to the invention,

FIGURE 2 is a section on line 22 of FIGURE 1,

FIGURE 3 is an end view of the housing body with one of the end plates and sealing gaskets, and

FIGURE 4 is a cross-section on line 44 of FIGURE 3, showing the pump with the housing end plates removed.

Referring now to the drawings, the pump comprises a housing body 1 which contains the usual gear chamber 2 constituted by two inter-penetrating parallel cylindrical bores 3 and 4 which respectively accommodate the intermeshing pumping gears 5 and 6, while flattened portions 7 and 8 in the zone of intersection of the gears form respectively an inlet chamber and an outlet chamber. A pump inlet bore 14 and a pump outlet bore 15 are arranged in the central plane of the pump body I and symmetrically to the plane containing the axes of the two bores 3 and 4. The diameter of bore 4 and gear 6 is ten percent greater than that of bore 3 and to its original one, f

engages gear 5, the gear having tenteeth, while gear 6 has I which is coupled to the gear 5' to transmit'power to the pump. T he two end members 9 and 10 are secured to the housing body 1 by bolts 12 and are located in relation to it by'dowels 13;'the bolts 12 and the dowels 13' are arranged symmetrically to the planecontaining the axes of the two gears. The axial length of the gears 5 and 6 is less than that of the housing body l, and the gear cavity 2 contains, in addition to the pumping gears, and at each side of the latter, a pairof side plates 16 1 and 17. The outer face of each of these plates is provided with a surface groove 18 which leads from a point at the edge of the plate, in a curved line encircling the journals 5a and 6a of the two pumping gears 5 and6,

' to a second point at the edge of the plate 16 or '17. This groove is continued by a groove 19 in the housing body 1 was to form jointly with the latter a closed path. 'I A round-section endless sealin'g gasket 20 is accommodated:

in the combined groove 18,19 and co-operate with the opposed surface of the housing end body 9 01' lttto iso late the zone on the surface of the side 'plate'which in-' eludes the outer ends of the bores through which the gear journals extend, and which communicates through a bevelled portion 21- of the side plate withthe pump in-' let 15, from the remainder of the outer surface of the pump side plate, which througha second bevel zz communicates with'the pump outlet 14. I I In addition to the groove '19 and symmetrically two pumping gears, the housing body contains a second to the I latter in relation to the plane containing the axes of the tion with the pump-inlet port, the pump may'alterna' tively be provided with a gasket which-encircles an area notcontaining either of the two journals and which is connected to the pump outlet instead of the pump inlet. The invention may be applied equally to gear-type mo- 7 tors as to gear pumps 'in the narrower sense, subject to -modifications which are obvious to those skilled in the art, for example to the effect that the chamber inside a gasket encir'cling the two, gear journals would in that case communicate with the motor outlet, instead of the pump inlet, sincein that case this is the low-pressure port.

Finally itwill be evident to those skilled in the art thatthe use of two pumping gears having relatively prime numbers of teeth maybe employed independently of the use of a symmetricalpurnp housing and vice versa if desired. r j l I What I claim is: V v

A gear pump comprising two intermeshing pumping gears each having at least one journal, and a housing body having 'a cavity in which the gears are rotatable about parallel axes, and' having bores extending from said cavity coxially, with the journals of each gear, where.- in the housing body comprisesat least two parts joined in a plane extending through said-cavity, said parts being provided with locating meansfor determining their accurate relative position, said cavity and locating means being symmetrical aboutat least two of three mutually "perpendicular planes of which one contains the axes of said gears, another is parallel to thesaid axes, and the third is perpendicular to the said'axes, so that the gears can be assembled with the housing bodyjiniat least two alternative positions,- in whichthe housing is turned relative'to thelgears about the line. of intersection of two planes ofsymmetry, and wherein the pump further comprises a pressure-loaded side plate'having two parallel plane surfaces one of which is applied to a side surface of identically dimensioned groove 19a, which in the illustrated position of the pump is not utilised.

When, after prolonged use, the surfaces of the bores adjacent to the inlet 15, towards which the gears are.

urged by the hydrostatic pressure, have been worn to V such an extentv as to unduly impair the volumetric efli f ciency can be restoredto approximately its original'value by dismantling the pump and reversing the housing body 1 about a line which extends perpendicularly-to the two moda'te part ofthe gasket 20, While the 'grooves 19 are unused; When the pump .is now operated,.tne pressure at the pump outlet, now constituted by the bo'relS, will urge the gears into contact with the portions of the bores j 10 and 11 adjacent to the bore 14, whichnow constitutes v the pump inlet, that is to say with portions of the bores 10 and 'llwhich up to then'have not been worn, so that after a fresh running-in period substantially the original volumetric efliciency of the pump is restored andthe spell of life substantially equal pump is given another While one embodiment of the pump according to the invention has been described in some detail with reference to the drawings, it-will be appreciated that the use of the invention is not restrictedto thisparticular form of pump. Thus the number of, gear teeth'ofthe two pumping gears may be made different without losing, the

the gears by the delivery pressure of the pump,'and in fwhich substantial alignment of the pressure forces acting on the two sides of the side plate is achieved by meansof a sealingjring or gasket which separates a zone in which pump-delivery pressure acts,"from a second 'zone under pump-inlet pressure, part of the length of-fsaid. ring heing accommodated in a groove formed in the other plane surface I of theQsttid side plateand interconnecting two 'pointsat the circumference of said side plate and two grooves, adapted to respectively accommodatethe remainder'of the sealing ring, being formed in the housing body to'respectively interconnect the pointsof the housr ing body, located oposite to said two points at the circumference ofthe'. side plate before and after reversal of "the pump housing body relative tothe gears.

' 2. Afgear; pump as claimed in claim 1 wherein the intermeshing pumping gears have numbers of teeth which are prime relative to each other, the housing body being so constructed as to enable it to be assembled with the gears in two alternative positions obtained by turned the housing body relative to the gears'about' an axis perpendicular to. and intersecting'the axes of the journals of a; both gears.

References Cited by the, Examiner V VUNITED STATESuPATENTS 2,620,553 Schultz 103'126 g 2,772,638 ,12/56, Nagley l03 126 2,809,592 10/57 Miller at al.* 103-126 2,816,510 12/57 Jarvis 2;; l03"-126 2,932,254 4/60 Booth et al. '103-126 3,057,302 10/62 Lockett 103-126 I .FOREIGNEPATENTS. 772,160 10/57 Great Britain.

r DONLEY J. STOCKING, Primary E aminer. 

1. A GEAR PUMP COMPRISING TWO INTERMESHING PUMPING GEARS EACH HAVING AT LEAST ONE JOURNAL, AND A HOUSING BODY HAVING A CAVITY IN WHICH THE GEARS ARE ROTATABLE ABOUT PARALLEL AXES, AND HAVING BORES EXTENDING FROM SAID CAVITY COXIALLY WITH THE JOURNALS OF EACH GEAR, WHEREIN THE HOUSING BODY COMPRISES AT LEAST TWO PARTS JOINED IN THE PLANE EXTENDING THROUGH SAID CAVITY, SAID PARTS BEING PROVIDED WITH LOCATING MEANS FOR DETERMINING THEIR ACCURATE RELATIVE POSITION, SAID CAVITY AND LOCATING MEANS BEING SYMMETRICAL ABOUT AT LEAST TWO OF THREE MUTUALLY PERPENDICULAR PLANES OF WHICH ONE CONTAINS THE AXES OF SAID GEARS, ANOTHER IS PARALLEL TO THE SAID AXES, AND THE THIRD IS PERPENDICULAR TO THE SAID AXES, SO THAT THE GEARS CAN BE ASSEMBLED WITH THE HOUSING BODY IN AT LEAST TWO ALTERNATIVE POSITIONS, IN WHICH THE HOUSING IS TURNED RELATIVE TO THE GEARS ABOUT THE LINE OF INTERSECTION OF TWO PLANES OF SYMMETRY, AND WHEREIN TE PUMP FURTHER COMPRISES A PRESSURE-LOADED SIDE PLATE HAVING TWO PARALLEL PLANE SURFACES ONE OF WHICH IS APPLIED TO A SIDE SURFACE OF THE GEARS BY THE DELIVERY OF THE PUMP, AND IN WHICH SUBSTANTIAL ALIGNMENT OF THE PRESSURE FORCES ACTING ON THE TWO SIDES OF THE SIDE PLATE IS ACHIEVED BY MEANS OF A SEALING RING OR GASKET WHICH SEPARATES A ZONE IN WHICH PUMP-DELIVERY PRESSURE ACTS, FROM A SECOND ZONE UNDER PUMP-INLET PRESSURE, PART OF THE LENGTH OF SAID RING BEING ACCOMMODATED IN A GROOVE FORMED IN THE OTHER PLANE SURFACE OF THE SAID SIDE PLATE AND INTERCONNECTING TWO POINTS AT THE CIRCUMFERENCE OF SAID SIDE PLATE AND TWO GROOVES, ADAPTED TO RESPECTIVELY ACCOMMODATE THE REMAINDER OF THE SEALING RING, BEING FORMED IN THE HOUSING BODY TO RESPECTIVELY INTERCONNECT THE POINTS OF THE HOUSING BODY LOCATED OPPOSITE TO SAID TWO POINTS AT THE CIRCUMFERENCE OF THE SIDE PLATE BEFORE AND AFTER REVERSAL OF THE PUMP HOUSING BODY RELATIVE TO THE GEARS. 